centos man page for blk_sync_queue

BLK_SYNC_QUEUE(9)						   Block Devices						 BLK_SYNC_QUEUE(9)

NAME
       blk_sync_queue - cancel any pending callbacks on a queue

SYNOPSIS
       void blk_sync_queue(struct request_queue * q);

ARGUMENTS
       q
	   the queue

DESCRIPTION
       The block layer may perform asynchronous callback activity on a queue, such as calling the unplug function after a timeout. A block device
       may call blk_sync_queue to ensure that any such activity is cancelled, thus allowing it to release resources that the callbacks might use.
       The caller must already have made sure that its ->make_request_fn will not re-add plugging prior to calling this function.

       This function does not cancel any asynchronous activity arising out of elevator or throttling code. That would require elevaotor_exit and
       blkcg_exit_queue to be called with queue lock initialized.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014							 BLK_SYNC_QUEUE(9)